In the field of medicine in which it is often necessary to inject a fluid, i.e., a solution containing certain nutrients or medications, or for the purpose of impurity exchange and removal, as in peritoneal dialysis, a severe problem exists due to infection caused by the injection of infection-causing microorganisms along with the solution. Examples of the injection of such solutions include intravenous injection of nutrients and/or medications and, as noted above, peritoneal dialysis. During intravenous injection, a solution bag containing the desired solution is connected through tubing and an intravenous needle directly into the vein of a patient. Peritoneal dialysis, which has the great advantage of using a small light-weight system which the patient can attach and detach on his own, outside of a hospital or doctor's office, involves the permanent installation in the patient of a body-penetrating apparatus, e.g., a cannula. The cannula penetrates the body and pierces the peritoneum with the body-penetrating end thereof opening into the peritoneal cavity. The external end of the cannula has an opening to which the patient can attach tubing connected to a suitable reservoir, e.g., an IV bag, for a dialysis solution. During the dialysis, the solution from the IV bag is gravity-drained through the tubing and the cannula into the peritoneal cavity. The tubing is then detached from the cannula and the solution allowed to remain in the peritoneal cavity for a period of time during which impurities from the bloodstream are removed through osmosis through the peritoneum. The patient then reattaches tubing to the cannula and the dialysis solution is drained by gravity from the peritoneal cavity, removing along wih the dialysis solution the impurities transferred to the solution through the peritoneum.
While IV's are normally administered to the patient in the sterile environment of, e.g., a hospital, at times the IV must be placed on the patient in the field, as, e.g., at the scene of an accident. In such cases, the danger exists of possibly introducing microorganisms into the IV bag or the tubing connecting the IV bag to the intravenous needle. In addition, even when the IV is administered to the patient in the sterile environment of the hospital or doctor's office, manufacturing errors during the fabrication of the IV bag, its solution contents, or the connecting tubing, also create some danger that microorganisms, which can cause infection, might be contained within the IV bag, its solution contents, or the tubing, or the connection between the tubing and the intravenous needle.
The problem of potential injection of infection-causing microorganisms is even more severe in the peritoneal dialysis situation. This potential infection-causing problem is presently the major drawback to the otherwise extremely beneficial advantages of peritoneal dialysis. Ailments which necessitate treatment through dialysis strike patients in all socio-economic levels and patients having widely varying degrees of intelligence and/or habits of cleanliness or the practice of taking sterile precautions when connecting the tubing for the dialysis solution to the external end of the cannula. The danger thus exists that patients, to varying degrees, will be susceptible to the injection of infection-causing microorganisms when making the necessary connections for self-administered peritoneal dialysis.
Filters for separating substances contained in a suspension in a fluid, e.g., a solution, have been well known in the medical arts. Mechanical filters constructed of a material such as cloth which will absorb certain materials, but not others, or filters using mechanical means, e.g., metal grating or metal particles and accomplishing filtration by limiting the size of the allowable particles which can pass through the mechanical restrictions, are also well known in the art. Filtration by ion exchange is also well known, in which a bed of filter elements which have certain ions loosely bound thereto and a stronger affinity for other ions desired to be removed from the solution, than the affinity for the loosely-bound ions, will exchange ions with the solution, thus removing the undesirable ions. In addition, various other filtrations, e.g., filtrations through chemical means, are known in the art.
In the past, microorganisms, e.g., bacteria, have been filtered in medical devices by mechanical means, e.g., by screening, or by chemical means, in which anti-bacterial agents, e.g., iodine, are placed in the path of the fluid from which the microorganisms are desired to be removed, e.g., by impregnating a cloth filter with antibacterial agents. The use of antiseptic techniques during patient treatment, including surgical gloves and clean and careful handling methods, are also techniques of preventing microorganisms from entering the body of the patient, i.e., "filtering" the microorganisms from entering an opening in the body.
It is also known in the art to use activated carbon which has been impregnated on its surface with silver during various sterilization and purification procedures well known in the medical arts. These methods of impregnating silver on the surface of activated carbon are shown, e.g., in U.S. Pat. No. 3,294,572. However, in the course of such usage, organic substances accumulate on the surface of the silver-impregnated material resulting in a large reduction in the silver impregnated material's capacity to effectively sterilize. In addition, the silver-impregnated carbon systems kill the microorganism, e.g., bacteria, via a sustained release of silver ions into the filtered solution. High concentrations of silver ion are needed to relatively rapidly kill the microorganisms, e.g., bacteria. This requires scavenger systems to be utilized to remove or sufficiently lower the silver ion concentration to physiologically safe levels prior to the introduction of any such filtered and sterilized solution into the body of a patient.
Mechanical filtering elements which have a sufficiently small porosity to filter microorganisms, e.g., micropore filters, would create such a substantial delay in the transfer of the IV or dialysis solution through the filter as to result in an exceedingly large time, on the order of days, for sufficient solution to be injected into the body of the patient to have the beneficial results desired.
The present invention, therefore, relates to a method and apparatus for removing living microorganisms from a fluid to be introduced in vivo, wherein the fluid is passed through a filter comprising a tubular passage having a plurality of filter elements coated with a microbicidal material, e.g., silver.
The problems enumerated in the foregoing discussion are not intended to be exhaustive, but rather are among many which tend to impair the effectiveness of methods and apparatus for injecting fluid in vivo, particularly when self-administered by the patient, and the use of known filter elements capable of removing microorganisms from such solution prior to injection. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that the prior art has not been altogether satisfactory.
Examples of the more important features of the present invention have been summarized rather broadly in order that the detailed description thereof that follows may be better understood and in order that the contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will also form the subject of the appended claims. These other features and advantages of the present invention will become more apparent with reference to the following detailed description of a preferred embodiment thereof in connection with the accompanying drawings, wherein like reference numerals have been applied to like elements, in which: